Sensor device

Patent metadata

Field	Value
Publication number	US-9287837-B2
Application number	US-201013392183-A
Country	US
Kind code	B2
Filing date	Aug 25, 2010
Priority date	Aug 26, 2009
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

A sensor device is provided with a voltage detection type sensor unit for converting a physical quantity into a voltage value and outputting a voltage signal indicating the voltage value; a chopper amplifier unit for generating a modulation signal by chopping the voltage signal output from the sensor unit with a predetermined chopping frequency, amplifying the modulation signal into an amplification signal, then demodulating the amplification signal and outputting it as an output signal; an integration unit including an operational amplifier, an input resistor connected to the inverting input terminal of the operational amplifier and a capacitor connected between the inverting input terminal and an output terminal of the operational amplifier; and a digital conversion unit for converting the output signal integrated by the integration unit into a digital signal.

First claim

The invention claimed is:

1. A sensor device, comprising:
a voltage detection type sensor for converting a physical quantity into a voltage value and outputting a voltage signal indicating the voltage value;
a chopper amplifier for generating a modulation signal by chopping the voltage signal output from the sensor with a predetermined chopping frequency, amplifying the modulation signal into an amplification signal, then demodulating the amplification signal and outputting the demodulated amplification signal as an output signal including noise components having the chopping frequency and odd number multiples frequency of the chopping frequency;
an integrator including an operational amplifier for amplifying a voltage difference between a voltage at a non-inverting input terminal and a voltage at an inverting input terminal, an input resistor connected to the inverting input terminal of the operational amplifier and a capacitor connected between the inverting input terminal and an output terminal of the operational amplifier and adapted to sample the output signal output from the chopper amplifier at a predetermined sampling frequency and integrate the sampled output signal;
a sampling frequency adjuster that reduces the noise components that pass the integrator by adjusting the sampling frequency so that the chopping frequency is an n-fold of the sampling frequency, where n is a natural number equal to or greater than 1;
the integration controller executes a control to generate the output signal integrated by the integrator by causing the operational amplifier to charge the capacitor by inputting the output signal output from the chopper amplifier to the inverting input terminal during a predetermined sampling period in every sampling cycle which is an inverse of the sampling frequency and causing the capacitor to discharge after the lapse of the sampling period; and
a digital converter for converting the output signal integrated by the integrator into a digital signal.

2. A sensor device according to claim 1 , further comprising:
an oscillator including a CR oscillation circuit having a resistor and a capacitor and adapted to generate clock pulses which are used to actuate the chopper amplifier and the integrator and serve as a basis for a pulse signal having the sampling frequency,
wherein the resistor and the capacitor of the oscillator have the same temperature characteristics as the input resistor and the capacitor of the integrator.

3. A sensor device according to claim 1 , further comprising:
an oscillator including a CR oscillation circuit having a resistor and a capacitor and adapted to generate clock pulses which are used to actuate the chopper amplifier and the integrator and serve as a basis for a pulse signal having the sampling frequency,
wherein the resistor and the capacitor of the oscillator have the same electrical characteristics as the input resistor and the capacitor of the integrator.

4. A sensor device according to claim 1 , further comprising:
a first storage and a second storage for storing a data of the output signal converted into the digital signal in the digital converter;
a cutoff portion for cutting off an output of the voltage signal from the sensor to the chopper amplifier;
a selector for selecting the first storage or the second storage to be stored the data of the output signal from the digital converter;
a controller for causing the data of the output signal that is converted into the digital signal in the digital converter to be stored in the first storage, with the cutoff portion cutting caused to cut off the output of the voltage signal from the sensor to the chopper amplifier and with the selector selecting the storage of the data of the output signal from the digital converter in the first storage, and for causing the data of the output signal that is converted into the digital signal in the digital converter to be stored in the second storage without the cutoff portion cutting off the output of the voltage signal from the sensor to the chopper amplifier and with the selector selecting the storage of the data of the output signal from the digital converter in the second storage; and
a subtractor for calculating a difference between the data of the output signal stored in the first storage and that of the output signal stored in the second storage.

5. A sensor device according to claim 4 ,
wherein the sensor and the chopper amplifier are connected by a plurality of signal lines for transmitting the voltage signal from the sensor;
the cutoff portion is a short-circuit switch for short-circuiting the plurality of signal lines;
the selector is a changeover switch for connecting either one of the first and second storages to the digital converter; and
the controller controls the selector and the cutoff portion such that the data of the output signal converted into the digital signal in the digital converter is stored in the second storage more frequently than in the first storage.

6. A sensor device according to claim 1 ,
wherein the integration controller executes a control to terminate an integration process when a voltage of the output signal output from the chopper amplifier reaches a predetermined reference voltage; and
the digital converter includes a time meter for measuring a time until the end of the integration process after the lapse of the sampling period in a digital value and outputting the measured time in the digital value as the digital signal.

7. A sensor device according to claim 6 ,
wherein the integration controller causes the capacitor to discharge by applying the reference voltage having a polarity opposite to that of a voltage of the output signal output from the chopper amplifier to the inverting input terminal after the lapse of the sampling period.

8. A sensor device according to claim 6 , further comprising:
an oscillator including a CR oscillation circuit having a resistor and a capacitor and adapted to generate clock pulses which are used to actuate the chopper amplifier and the integrator and serve as a basis for a pulse signal having the sampling frequency,
wherein the resistor and the capacitor of the oscillator have the same temperature characteristics as the input resistor and the capacitor of the integrator; and
the integration controller controls charging and discharging of the capacitor of the operational amplifier based on the pulse signal.

9. A sensor device according to claim 6 , further comprising:
an oscillator including a CR oscillation circuit having a resistor and a capacitor and adapted to generate clock pulses which are used to actuate the chopper amplifier and the integrator and serve as a basis for a pulse signal having the sampling frequency,
wherein the resistor and the capacitor of the oscillator have the same electrical characteristics as the input resistor and the capacitor of the integrator; and
the integration controller controls charging and discharging of the capacitor of the operational amplifier based on the pulse signal.

Assignees

• Lau Choon How
• Kumahara Minoru
• Panasonic Ip Man Co Ltd

Inventors

• Lau Choon How
• Kumahara Minoru

Classifications

• H03F2200/78

  A comparator being used in a controlling circuit of an amplifier · CPC title

• H03F3/393 Primary

  with field-effect devices · CPC title

• H03F3/45475

  using IC blocks as the active amplifying circuit · CPC title

• H03F2200/264

  An operational amplifier based integrator or transistor based integrator being used in an amplifying circuit · CPC title

• H03F2200/261

  Amplifier which being suitable for instrumentation applications · CPC title